can't seem to perform a P-Delta analysis

[rkiseral]

I am attempting to do a P-Delta analysis of a vertical bar with a significant point mass at the top and a transverse force at the bar top causing some bending and deflection in the bar.

To wit: a 1 inch diameter bar 20 inches long in the vertical (+Z) direction.  Base is fixed with DOF restrained.  At the top is a point mass of, say, 200 lbf. (perhaps approximated by setting the density of the topmost frame element to be quite large.)  A point force of, say,  100 lbf is acting in the X direction at the topmost node, applied gradually ramping up from 0 to 100 lbf in 10 load steps.  As the top of the bar displaces, the gravity force (assumed in the -Z direction) on the displaced point mass acts to cause a secondary moment which exacerbates the bending.

From what I can tell, FEAPpv allows body forces but notes that if proportional loads are present the body forces get multiplied by the total proportional loading factor (page 102 of the FEAP User Manual).

I would like to apply a gravity load on the elements in the -Z direction to my model and keep it constant while specifying a proportional point load in the X direction at the top node.  I don't see how to do that.  Am I missing something here, or is that something that FEAPpv doesn't allow?

Thanks in advance for any insight that you may care to offer.

[M. Kurdi]

If you are carrying static analysis then the density (weight) of the frame element will not be accounted for. You can probably simulate the 200 lbf mass at the top with a compressive force of 200 lbf acting in -Z at top of the rod. Would this work instead?

[Prof. R.L. Taylor]

First, feap and feappv have a point element that allow for point mass to be included (see pointnd.f in the /elements directory of feappv).  What element are you using for the beam?  Some do have body forces.